. D CR Nomenclature D 1

. D CR Nomenclature D 1

Appendix D: CR NOMENCLATURE D 2 The notation used by different investigators working in CR formulations has not coalesced, since the topic is in flux. This Appendix identifies the symbols used in the present book. General scheme of notation is Non-bold letters: scalars. Uppercase bold letters (roman and greek): matrices and tensors. Lowercase bold letters (roman and greek): column vectors, but there are occasional exceptions such as X and Y. Symbol Meaning a As subscript: generic nodal index b As subscript: generic nodal index b i Components of Rodrigues-Cayley axial vector. c i Generic coefficients. Components of vector c. d As subscript: deformational e Base of natural logarithms. As superscript: element index. e ij Strains. f i Components of force vector f h i Triangle heights. i As subscript: generic index. Imaginary unit in complex numbers. j As subscript: generic index k As superscript: iteration count l As subscript: generic index m As subscript: generic index n As subscript: incremental step number n i Components of vector n. p i Quaternion components. r As subscript: rigid s kx, s ky Projections of triangle side L k on {x, y} axes. t Time. u Displacement magnitude u i, ũ i, ū i Displacement components in x i, x i, x i axes, respectively. u di, ũ di, ū di Deformational displacement components in x i, x i, x i axes, respectively. u ri, ũ ri, ū ri Rigid displacement components in x i, x i, x i axes, respectively. x x 1 axis when using {x, y, z} notation x i Components of global-frame position vector x x i Components of element base-frame position vector x. x i Components of element CR-frame position vector x. y x 2 axis when using {x, y, z} notation z x 3 axis when using {x, y, z} notation A Area. C Generic centroid of body or element in statics. Center of mass in dynamics. C 0,C R,C Body or element centroid in base, CR and deformed configurations, respectively. L Length of 2-node element. Generic length. L k Length of triangle side opposite node k. N Number of structure nodes. N e Number of nodes of element e. D 2

D 3 O Origin of global frame. T Kinetic energy U Internal energy, strain energy. W External work. X x 1 axis when using {X, Y, Z} notation X i Material global Cartesian axes Y x 2 axis when using {X, Y, Z} notation Z x 3 axis when using {X, Y, Z} notation a Position vector of C 0 from origin of global frame. Generic vector. b Position vector of C R C from origin of global frame. Generic vector. c Displacement of base element centroid C 0 to C R C. d Deformational displacement. Array of nodal DOF, collecting translations and rotations. d Array of nodal deformational DOF, collecting translations and rotations. e Strains arranged as vector. f Generic force vector. External force vector. f External force vector in element CR frame. f b Balance (self-equilibrated) force vector. f u Unbalanced (out of equilibrium) force vector. i Base unit vector m Generic nodal moment vector. m a Nodal moment components at node a. n Unit normal. Direction of rotation vector in 3D. n a Translational force components at node a. 0 Null matrix or vector. p Internal force vector of structure. p e Element internal force vector in global frame. p e Element internal force vector in CR frame. q Not used r Force residual vector. u Displacement vector. Also generic vector: meaning from context. v Denotes vector collecting nodal displacements and rotations, displacements and spins, or displacements and rotators. See Table D.2. Also generic vector: meaning from context. w Generic vector: meaning from context. ˆv Global DOF vector for complete structure. x Global-frame spatial position vector. x Element base-frame position vector. x Element CR-frame position vector. x Frame independent position vector. y Alternative notation for position vector. Generic vector. y Frame independent position vector. z i Spinor eigenvector. A Generic matrix. Matrix relating strains to deformational displacements. Generic matrix. B d D 3

Appendix D: CR NOMENCLATURE D 4 C Strain-stress (compliance) matrix D Diagonal matrix of zeros and ones. Generic diagonal matrix, size from context. E Stress-strain (elasticity) matrix F Generic matrix function F n, F nm Auxiliary matrices in tangent stiffness derivations. G Element spin-fitter matrix linking δωr e to δve. G a Component of G associated with node a. H Block diagonal matrix built with H a and I blocks. H a Evaluation of H(θ) at node a. H(θ) Jacobian of θ with respect to ω. I Identity matrix, size from context. J Jacobian matrix in general. J ab Jacobian matrix relating quantities at nodes a and b. K Tangent stiffness matrix of structure. K e Element tangent stiffness matrix in global frame. K e Linear element stiffness matrix in local CR frame. K e R Element tangent stiffness matrix in local CR frame. K GM Moment correction geometric stiffness matrix. K GP Equilibrium projection geometric stiffness matrix. K GR Rotational geometric stiffness matrix. K M Material stiffness matrix. L Block diagonal built with L a and 0 blocks. L a Evaluation of L(θ, m) at node a. L(θ, m) Contraction of H(θ) T / ω) with vector m M Mass matrix. N Spinor for vector n. P Projector matrix. P u Translational projector matrix, a.k.a. T-projector. P ω Rotational projector matrix, a.k.a. R-projector. Q Generic orthogonal matrix. R Orthogonal rotation matrix: the matrix representation of a rotator. R 0 Transformation rotator between element base frame and CR frame. R 0, R 0 Rotator R 0 referred to element base and CR frames, respectively. S Spin-lever (a.k.a. moment-arm) matrix built up of S a blocks. Generic skew-symmetric matrix. S a Spin-lever matrix for node a. T Element CR-to-global transformation matrix built from T R blocks. T 0 Transformation rotator from element base frame to global frame. T R Transformation rotator from element CR frame to global frame. U ab Building block of translational projector P u. V Generic skew-symmetric matrix. W Generic skew-symmetric matrix. X Global position vector with X i as components. X Coordinate free material position vector. X Element base position vector with x i as components. D 4

D 5 X Element CR position vector with x i as components. Y Position vector collecting y i as components. Z Matrix of right eigenvectors of spinor. α Coefficient in parametrized rotator representation. β Coefficient in parametrized rotator representation. γ Spinor normalization factor. δ Variation symbol. δ ab Kronecker delta. ɛ Small scalar ζ i Triangular coordinates η Coefficient in H(θ). θ Rotation angle in general. Magnitude of rotation vector θ. κ Curvature λ Lagrange multiplier µ Coefficient in L(θ, m). ν Poisson s ratio ρ Mass density. σ ij Stresses. τ Coefficient in Log e (R) formula. χ,φ,ϕ,ψ Generic angle symbols. ψ Generic angle. ω Magnitude of spin vector ω. Summation symbol. a, b Abbreviations for N e a=1 and N e b=1. θ Rotation axial vector (a.k.a. rotation pseudovector). φ Axial vector built from φ i angles. ψ Axial vector built from ψ i angles. σ Stresses arranged as vector. σ 0 Initial stresses (in the base configuration) arranged as vector. ω Spin axial vector (a.k.a. spin pseudovector). Γ Auxiliary matrix used in the decomposition of G Θ Spinor built from rotation axial vector. Λ Diagonal matrix of eigenvalues of Ω. Ξ Auxiliary matrix used in the decomposition of G. Φ Spinor built from axial vector φ. Ψ Spinor built from axial vector ψ. Σ Spinor built from the Rodrigues-Cayley parameters b i. Ω Spinor built from spin axial vector ω. Ω p Spinor build from quaternion parameters p i. C Configuration: see Table D.1 for further identification by superscripts. CR Abbreviation for corotational (a.k.a. corotated) kinematic description. DOF Abbreviation for degree of freedom. EICR Abbreviation for Element Independent Corotational formulation. Rotator Abbreviation for rotation tensor (or 3 3 rotation matrix). D 5

Appendix D: CR NOMENCLATURE D 6 Spinor Abbreviation for spin tensor (or 3 3 spin matrix). TL Abbreviation for Total Lagrangian kinematic description. UL Abbreviation for Updated Lagrangian kinematic description. (.) Abbreviation for d(.)/dt (.) 0 or (.) 0 (.) pertains to base (initial) configuration C 0. (.) D or (.) D (.) pertains to deformed configuration C D. (.) G or (.) G (.) pertains to globally aligned configuration C G. (.) R or (.) R (.) pertains to corotated configuration C R. (.) d (.) is deformational. (.) e (.) pertains to element e. (.) r (.) is rigid. () T Matrix or vector transposition. () 1 Matrix inverse. axial(.) Extraction of axial vector from skew-symmetric matrix argument e (.) Matrix exponential if (.) is a square matrix Exp(.) Alternative form for matrix exponential Log e (.) Matrix natural logarithm Rot(.) Construction of rotator from spinor argument Skew(.) Extraction of spinor from rotator argument Spin(.) Construction of spinor from axial vector argument trace(.) Sum of diagonal entries of matrix argument D 6